The present invention relates to a compound electromagnetic valve, a high pressure pump that uses the compound electromagnetic valve, and an apparatus for controlling the high pressure pump.
A typical internal combustion engine includes a high pressure fuel pump, which is connected to an electromagnetic valve. The electromagnetic valve controls the flow of fuel that is supplied to the high pressure pump. The electromagnetic valve includes a valve body, which is urged by a spring. The valve body adjusts the opening of a fuel passage. When the valve is closed, the valve body as pressed against a valve seat not only by the force of the spring but also by a force based on the difference between the pressures acting on opposite sides of the valve body. Thus, when opening the valve again, a force that is large enough to separate the valve body from the valve seat against the force based on the pressure difference must be applied to the valve body. This requires a relatively large electromagnetic valve and a relatively high electric current.
To solve this problem, an electromagnetic valve having two valve bodies was introduced in Japanese Unexamined Utility Model Publication No. 60-47874. The electromagnetic valve of the publication includes a first valve body and a second valve body for controlling the opening of a fuel passage. The first valve body is cylindrical and accommodates the second valve body. The second valve body selectively closes a fuel bleed passage, which is formed in the first valve body. The valve also includes a solenoid that directly actuates only the second valve body. The second valve body is separated from the first valve body to open the bleed passage. Thereafter, when the second valve body is moved by a predetermined distance, the second valve body is engaged with the first valve body, which causes the first valve body to open the fuel passage. Since the second valve body first opens the bleed passage, the pressure difference across the first valve body is eliminated. Thus, the force required for opening the fuel passage is reduced. Accordingly, the size of the electromagnetic valve and the level of the current supplied to the valve are reduced.
However, since movement of the first valve body is dependent on movement of the second valve body, the opening of the fuel passage cannot be finely controlled. Thus, the following functions cannot be achieved by the electromagnetic valve of the publication. For example, depending on the condition of the high pressure fuel pump, fine adjustment of the fuel flow must be accomplished by controlling the opening of the bleed passage. In this case, only the second valve body must be controlled. In another condition, the fuel flow must be quickly increased. In this case, the first valve body must open the fuel passage immediately after the second valve body opens the bleed passage, that is, the first and second valve bodies must be moved substantially at the same time. In another condition, the period from when the second valve body opens the bleed passage to when the first valve body opens the fuel passage must be extended such that the pressure difference across the first valve body is reliably eliminated.
Accordingly, it is an objective of the present invention to provide an electromagnetic valve having compound valve bodies that finely controls the opening of a passage. Other objectives are to provide a high pressure pump that uses the electromagnetic valve for finely controlling the fluid flow and to provide an apparatus for controlling the high pressure pump.
To achieve the above objective, the present invention provides an electromagnetic control valve comprises a passage for conducting fluid. An electromagnetic actuator generates an electromagnetic force. A main valve body opens and closes the passage in accordance with the electromagnetic force generated by the electromagnetic actuator. A bypass is formed in the main valve body. A sub valve body opens and closes the bypass in accordance with the electromagnetic force generated by the electromagnetic actuator. The electromagnetic force generated by the electromagnetic actuator is adjusted such that the sub valve body is opened and closed while the main valve body closes the passage.
The present invention also provides a high pressure pump. The high pressure pump comprises a high pressure chamber A passage supplies fluid to the high pressure chamber. An electromagnetic control valve controls the amount of fluid that enters the high pressure chamber through the passage. the electromagnetic control valve comprises an electromagnetic actuator for generating an electromagnetic force. A main valve body opens and closes the passage in accordance with the electromagnetic force generated by the electromagnetic actuator. A bypass is formed in the main valve body. The bypass connects an upstream part of the main valve body to a downstream part of the main valve body. A sub valve body opens and closes the bypass in accordance with the electromagnetic force generated by the electromagnetic actuator. The electromagnetic force generated by the electromagnetic actuator is adjusted such that the sub valve body is opened and closed while the main valve body closes the passage.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.